Wetzel

Math 155

2.1 – Basic Set Concepts

Vocabulary Terms –

            Set:      a collection of information or objects.  A set is named by a capital letter and is written in braces, .

            Element:           an object or piece of information in a set.  Also called a data item.

            Well-defined set:           a set whose contents can be clearly determined.

3 Ways to Write or Define a Set –

            1.  Word Description:              

                        Set B are the months of the year beginning with the letter J.

            2.  Roster Notation:

            3.  Set-Builder Notation:

            Ex.:      p. 55 #1 – 32.

Natural Numbers, N –

                        N =

Empty Set –

            also called the null set is a set that contains no elements.

            written as  or

            Ex.:  p. 56 #33 - 46

Notations -

                     “is an element of”

                     “is not an element of”

            Ex.:      p.56  #47 – 66

Cardinal Number of a set A –

            is the number of distinct elements in a set. (the number of non-repeating elements)

            written  and read “n of A”

            Ex.:  p.56 #67 – 80

Equivalent Sets –

            Sets are equivalent if the contain the same number of elements. (they have the same cardinal numbers)

Equal Sets –

            Sets are equal if the contain the exact same elements regardless of order or repetition.

                        A = B

            Ex.:  p.56 #81 – 90

Finite and Infinite Sets –

            Finite Set:  A set with a countable number of elements.

            Infinite Set:  A set with an infinite number of elements.

            Ex.:  p.56 #91 – 96

HW:  p.55 #1 – 95 every 4^th problem (1, 5, 9, 13, ….)